Recent scientific discoveries show that the Amazon rainforest might control the climate for much of South America. The theory could mean even more disastrous ramifications for the fragile ecosystem if deforestation continues unabated.

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Transcript

STEVE INSKEEP, HOST:

South America's endangered Amazon rain forest may be even more vital than we thought. That forest is going away, slash and burned at an astonishing rate.

LINDA WERTHEIMER, HOST:

We've been listening in recent days to the war over what remains. And that's not really a metaphor. The fight sometimes involves gunfire.

INSKEEP: This forest produces so much oxygen that it's called the lungs of the earth. And a new theory suggests that that actually understates the value of the rain forest. Here's NPR's Lourdes Garcia-Navarro.

LOURDES GARCIA-NAVARRO, BYLINE: Take yourself back to middle school. You're sitting in class, maybe a bit bored, probably kind of sleepy. The lights get turned down. The teacher pops in a documentary that goes something like this.

(SOUNDBITE OF DOCUMENTARY)

UNIDENTIFIED NARRATOR: The Amazon, it's the lungs of the planet.

GARCIA-NAVARRO: It's probably the thing most people remember about the Amazon.

(SOUNDBITE OF PERSON BREATHING)

GARCIA-NAVARRO: And indeed, this vast tract of trees does turn carbon dioxide into glucose and oxygen, the very air we breathe. But the rain forest isn't just the lungs of the world.

(SOUNDBITE OF HEARTBEAT)

GARCIA-NAVARRO: A new theory suggests it's also its beating heart.

ANTONIO NOBRE: It's a pump. It's been called the biotic pump.

GARCIA-NAVARRO: Antonio Nobre is one of the leading climate scientists in Brazil. We're sitting outside on a sunny morning at Brazil's National Institute for Space Research, where he works. He talks with expressive hand gestures and sound effects.

NOBRE: We slept with the sounds of owls (imitating owl hooting).

GARCIA-NAVARRO: He's speaking about how his dad brought him up in the countryside near Brazil's biggest city, Sao Paulo, listening to nature and observing it. Ever since, he's been fascinated by and studying the rain forest. He's 57, and his brothers are also famous scientists in Brazil. So it's a family business, if you will. Lately, he's been doing a lot of work on how deforestation is affecting the rain forest and the climate. This pump theory came out of his curiosity.

NOBRE: How is it possible that the Amazon rain forest has been around for more than 50 million years? I posed the challenge, how could the Amazon have stood for geological time without having a mechanism of producing its own rain?

GARCIA-NAVARRO: Two Russian physicists came up with a proposed explanation. Nobre says what they discovered is that the trees in the Amazon aren't just trees.

NOBRE: They compare the trees with geysers.

GARCIA-NAVARRO: The Amazon rain forest sucks water from the ground and releases the moisture into the atmosphere through a process called transpiration.

NOBRE: Transpiration is evaporation. But it's evaporation of water that went through the tree.

GARCIA-NAVARRO: Think of it like blood in our veins. But unlike blood, the tree water is then pushed up into the sky in a kind of water vapor.

NOBRE: This huge flow of vapor into the atmosphere is like an irrigation upside down. It's the rivers of rainfall.

GARCIA-NAVARRO: What it creates, Nobre says, are these massive, invisible flying rivers.

NOBRE: We did a calculation for the entire Amazon. We came with a number that is 20 billion tons of water evaporated per day in the Amazon basin.

GARCIA-NAVARRO: To put that number into perspective...

NOBRE: It's more than what the Amazon River discharges in the Atlantic in the same period, in one day.

GARCIA-NAVARRO: So why does the Amazon ecosystem do that? Well, the pump theory hypothesis says that the water vapor lowers the pressure above the rain forest, sucking in moisture from the oceans. So in effect, the rain forest is creating its own rain. When there's a drought, for example, the forest transpires even more. He uses a metaphor to explain.

NOBRE: You know, it's like love. Love is the only quantity that increases the more you give. And so the trees do this, lower the pressure during a drought, pull the moisture from the oceans and counter the droughts.

GARCIA-NAVARRO: This theory is still being hotly debated, though some recent studies support it. According to Nobre, the biotic pump action explains why the rain forest has survived all these years. Except, Nobre says, for right now.

NOBRE: When you come with the chainsaw and the bulldozer and fire, then forest doesn't know how to handle this. That's what I call the Achilles' heel of the rain forest.

GARCIA-NAVARRO: The problem for climate is that the trees, according to the pump theory, need to work together to create these movements of moisture in the air.

NOBRE: I've been witness of the most serious episode of destruction in one go, you know? In Brazil alone - and Brazil has only 65 percent of the Amazon - we have destroyed more than 40 billion trees - billion - six trees per human being on the face of the earth.

GARCIA-NAVARRO: Nobre released a report last year looking at over 200 peer-reviewed studies, across disciplines, to figure out what effect the cutting down of trees in the Amazon is having.

NOBRE: Even in a year that was very wet, still she saw incredible number of fires breaking into the rain forest. This is a very, very alarming sign that the system is failing - failing. It means multiple organ failure, like in an intensive care unit.

GARCIA-NAVARRO: Which is possibly why we could be seeing some places in South America facing severe drought right now. That regular pulling in of moisture from the oceans could affect the climate of the entire region, what areas get water that can grow food, for example, and what places can't.

NOBRE: There are many areas in the world that had forests and today are deserts. Saudi Arabia used to be lush forest a few thousand years ago.

GARCIA-NAVARRO: So he has this plea. Brazil has just committed to having zero deforestation by 2030. That in 15 years. It will be too late, he says.

NOBRE: Our livelihoods depend on the proper functioning of that biodiversity.

GARCIA-NAVARRO: He has been called alarmist. But he says he hopes the world is indeed alarmed.

NOBRE: Many colleagues of mine think it's too late; there's nothing more to be done.

GARCIA-NAVARRO: But he says he has hope. The rain forest, he says, has an enormous capacity to heal.

NOBRE: Chinese saying says, the best time to plant a tree was 20 years ago. The second best time's today. If we haven't done it, now is time to do it.